Cytokines are a group of proteinaceous signaling compounds that are used extensively for inter-cell communication. These compounds are critical to the functioning of both innate and adaptive immune responses. Apart from their importance in the development and functioning of the immune system, cytokines play a major role in a variety of immunological, inflammatory and infectious diseases.
Cytokines are produced by wide variety of cell types (both haemopoietic and non-haemopoietic) and can have effects on both nearby cells or throughout the organism, sometimes strongly dependent on the presence of other chemicals and cytokines.
Each cytokine generally binds to a specific cell-surface receptor. Subsequent cascades of intracellular signaling then alter cell functions. This may include the upregulation and/or downregulation of several genes and their transcription factors, in turn resulting in the production of other cytokines, an increase in the number of surface receptors for other molecules, or the suppression of their own effect by feedback inhibition.
Chemokine refers to a specific class of cytokines that mediate chemoattraction (chemotaxis) between cells. These chemokines are pro-inflammatory activation-inducible cytokines that generally have a molecular mass of between 8 and 10 kDa. Their receptors are mainly integral membrane proteins containing seven membrane-spanning helices, which are coupled to G proteins.
Chemokines are released from a wide variety of cells in response to bacterial infection, viruses and agents that cause physical damage. They function mainly as chemoattractants for leukocytes, recruiting monocytes, neutrophils and other effector cells from the blood to the sites of infection or damage. They can be released by many different cell types and serve to guide cells involved in innate immunity and also the lymphocytes of the adaptive immune system. Some chemokines also have roles in the development of lymphocytes, migration and angiogenesis.
As the cytokines and chemokines are involved in a multitude of different diseases and pathogenic or deleterious conditions, there is a general need of being able to effect or modulate the expression and/or release of these compounds. Furthermore, such release/expression modulation should preferably be selective in terms of only affecting a limited number of target cytokines or chemokines.
Document [1] investigates the effect of titanium surfaces on macrophage activation and secretion of proinflammatory cytokines and chemokines. When attached to rough titanium surfaces, lipopolysaccharide (LPS) stimulated macrophages increased their secretion of the cytokines interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) and the chemokines monocyte chemoattractant protein-1 (MIP-1) and macrophage inflammatory protein-1α (MCP-1α).
Document [2] discloses that titanium particles stimulate the selective induction of IL-8 and MCP-1 chemokines in human osteblast-like osteosarcoma cells.
Document [3] investigates the effect of titanium particles on cytokine release by macrophage-like cells (MLC). Titanium particles significantly enhanced MLC release of IL-1β, IL-8 and TNF-α.
Document [4] provides an overview of macrophage interactions with modified material surfaces. The document discloses that macrophages contacted with modified surfaces release of IL-1β, IL-6, IL-10 and TNF-α.